Table 2.

Disc degeneration grade based on Pfirrmann classification and facet degeneration grade based on Grogan classification

Grade	Disc degeneration grade based on Pfirrmann classification				Facet degeneration grade based on Grogan classification
	Disc structure	Distinction between nucleus and annulus	Signal intensity of disc	Disc height	Facet osteophyte	Facet cartilage	Facet subchondral sclerosis
I	Homogenous, white	Clear	Hyperintense, isointense to CSF	Normal	No osteophyte	Uniform thin band of cortical bone	Uniformly thick
II	In homogeneous, ±horizontal bands	Clear	Hyperintense, isointense to CSF	Normal	Possible or small osteophyte	Thin band of cortical bone that extended into the space from the articular surface	Eroded or irregular
III	Inhomogeneous, gray	Unclear	Intermediate	Normal to slightly decreased	Definite and moderate osteophyte	Dense bone that extended into the joint space but covered less than half the facet	Incompletely covering
IV	Inhomogeneous, gray to black	Lost	Intermediate to hypointense	Normal to slightly decreased	Large osteophyte	Covered greater than half the facet joint	Complete absence of cartilage
V	Inhomogeneous, black	Lost	Hypointense	Collapsed	-	-	-

CSF, cerebrospinal fluid.